EP3438162A1 - Highly absorbent resin and method for producing same - Google Patents
Highly absorbent resin and method for producing same Download PDFInfo
- Publication number
- EP3438162A1 EP3438162A1 EP17883446.1A EP17883446A EP3438162A1 EP 3438162 A1 EP3438162 A1 EP 3438162A1 EP 17883446 A EP17883446 A EP 17883446A EP 3438162 A1 EP3438162 A1 EP 3438162A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- polymer
- meth
- super absorbent
- acrylate
- absorbent polymer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 26
- 239000002250 absorbent Substances 0.000 title description 7
- 230000002745 absorbent Effects 0.000 title description 7
- 239000011347 resin Substances 0.000 title 1
- 229920005989 resin Polymers 0.000 title 1
- 229920000247 superabsorbent polymer Polymers 0.000 claims abstract description 112
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 75
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 71
- 239000000843 powder Substances 0.000 claims abstract description 61
- 239000000178 monomer Substances 0.000 claims abstract description 57
- 238000010521 absorption reaction Methods 0.000 claims abstract description 52
- 229920005601 base polymer Polymers 0.000 claims abstract description 48
- 239000011780 sodium chloride Substances 0.000 claims abstract description 40
- 239000000243 solution Substances 0.000 claims abstract description 34
- 229920006037 cross link polymer Polymers 0.000 claims abstract description 32
- 239000002504 physiological saline solution Substances 0.000 claims abstract description 25
- 230000002378 acidificating effect Effects 0.000 claims abstract description 12
- 239000007864 aqueous solution Substances 0.000 claims abstract description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 10
- 125000004432 carbon atom Chemical group C* 0.000 claims abstract description 9
- 239000000499 gel Substances 0.000 claims description 94
- 229920000642 polymer Polymers 0.000 claims description 92
- 239000000017 hydrogel Substances 0.000 claims description 84
- 238000010298 pulverizing process Methods 0.000 claims description 73
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 claims description 60
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 50
- 239000002245 particle Substances 0.000 claims description 37
- 238000001035 drying Methods 0.000 claims description 32
- 238000004132 cross linking Methods 0.000 claims description 29
- 238000006116 polymerization reaction Methods 0.000 claims description 27
- 239000000203 mixture Substances 0.000 claims description 18
- -1 acryloyl propane sulfonic acid Chemical compound 0.000 claims description 14
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 12
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 claims description 12
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 12
- 150000001875 compounds Chemical class 0.000 claims description 10
- 229920001223 polyethylene glycol Polymers 0.000 claims description 10
- 230000014759 maintenance of location Effects 0.000 claims description 8
- 239000002202 Polyethylene glycol Substances 0.000 claims description 7
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 6
- 125000003903 2-propenyl group Chemical group [H]C([*])([H])C([H])=C([H])[H] 0.000 claims description 5
- 150000003839 salts Chemical class 0.000 claims description 5
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims description 4
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 claims description 4
- PUPZLCDOIYMWBV-UHFFFAOYSA-N (+/-)-1,3-Butanediol Chemical compound CC(O)CCO PUPZLCDOIYMWBV-UHFFFAOYSA-N 0.000 claims description 3
- MYWOJODOMFBVCB-UHFFFAOYSA-N 1,2,6-trimethylphenanthrene Chemical compound CC1=CC=C2C3=CC(C)=CC=C3C=CC2=C1C MYWOJODOMFBVCB-UHFFFAOYSA-N 0.000 claims description 3
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 3
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 3
- LCZVSXRMYJUNFX-UHFFFAOYSA-N 2-[2-(2-hydroxypropoxy)propoxy]propan-1-ol Chemical compound CC(O)COC(C)COC(C)CO LCZVSXRMYJUNFX-UHFFFAOYSA-N 0.000 claims description 3
- TXBCBTDQIULDIA-UHFFFAOYSA-N 2-[[3-hydroxy-2,2-bis(hydroxymethyl)propoxy]methyl]-2-(hydroxymethyl)propane-1,3-diol Chemical compound OCC(CO)(CO)COCC(CO)(CO)CO TXBCBTDQIULDIA-UHFFFAOYSA-N 0.000 claims description 3
- 239000004743 Polypropylene Substances 0.000 claims description 3
- ZJCCRDAZUWHFQH-UHFFFAOYSA-N Trimethylolpropane Chemical compound CCC(CO)(CO)CO ZJCCRDAZUWHFQH-UHFFFAOYSA-N 0.000 claims description 3
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 claims description 3
- 235000011187 glycerol Nutrition 0.000 claims description 3
- ACCCMOQWYVYDOT-UHFFFAOYSA-N hexane-1,1-diol Chemical compound CCCCCC(O)O ACCCMOQWYVYDOT-UHFFFAOYSA-N 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- UWHCKJMYHZGTIT-UHFFFAOYSA-N tetraethylene glycol Chemical compound OCCOCCOCCOCCO UWHCKJMYHZGTIT-UHFFFAOYSA-N 0.000 claims description 3
- JAHNSTQSQJOJLO-UHFFFAOYSA-N 2-(3-fluorophenyl)-1h-imidazole Chemical compound FC1=CC=CC(C=2NC=CN=2)=C1 JAHNSTQSQJOJLO-UHFFFAOYSA-N 0.000 claims description 2
- 125000000954 2-hydroxyethyl group Chemical group [H]C([*])([H])C([H])([H])O[H] 0.000 claims description 2
- AUZRCMMVHXRSGT-UHFFFAOYSA-N 2-methylpropane-1-sulfonic acid;prop-2-enamide Chemical compound NC(=O)C=C.CC(C)CS(O)(=O)=O AUZRCMMVHXRSGT-UHFFFAOYSA-N 0.000 claims description 2
- MJIFFWRTVONWNO-UHFFFAOYSA-N 3-oxopent-4-ene-1-sulfonic acid Chemical compound OS(=O)(=O)CCC(=O)C=C MJIFFWRTVONWNO-UHFFFAOYSA-N 0.000 claims description 2
- SVYPQURSUBDSIQ-UHFFFAOYSA-N 4-methyl-3-oxopent-4-ene-1-sulfonic acid Chemical compound CC(=C)C(=O)CCS(O)(=O)=O SVYPQURSUBDSIQ-UHFFFAOYSA-N 0.000 claims description 2
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 2
- 125000003277 amino group Chemical group 0.000 claims description 2
- 125000000129 anionic group Chemical group 0.000 claims description 2
- 239000003125 aqueous solvent Substances 0.000 claims description 2
- LDHQCZJRKDOVOX-NSCUHMNNSA-N crotonic acid Chemical compound C\C=C\C(O)=O LDHQCZJRKDOVOX-NSCUHMNNSA-N 0.000 claims description 2
- 239000001530 fumaric acid Substances 0.000 claims description 2
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 claims description 2
- LVHBHZANLOWSRM-UHFFFAOYSA-N methylenebutanedioic acid Natural products OC(=O)CC(=C)C(O)=O LVHBHZANLOWSRM-UHFFFAOYSA-N 0.000 claims description 2
- 150000005846 sugar alcohols Polymers 0.000 claims description 2
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 claims description 2
- LDHQCZJRKDOVOX-UHFFFAOYSA-N trans-crotonic acid Natural products CC=CC(O)=O LDHQCZJRKDOVOX-UHFFFAOYSA-N 0.000 claims description 2
- 239000007788 liquid Substances 0.000 abstract description 16
- 230000035699 permeability Effects 0.000 abstract description 16
- 230000001747 exhibiting effect Effects 0.000 abstract description 6
- 238000000034 method Methods 0.000 description 33
- 230000000704 physical effect Effects 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 17
- 239000003505 polymerization initiator Substances 0.000 description 15
- 230000008569 process Effects 0.000 description 10
- 238000012719 thermal polymerization Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000000463 material Substances 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 6
- 239000003999 initiator Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 238000000691 measurement method Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000000470 constituent Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 238000006386 neutralization reaction Methods 0.000 description 4
- 239000002904 solvent Substances 0.000 description 4
- 239000004583 superabsorbent polymers (SAPs) Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000004745 nonwoven fabric Substances 0.000 description 3
- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 3
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 2
- XLLIQLLCWZCATF-UHFFFAOYSA-N 2-methoxyethyl acetate Chemical compound COCCOC(C)=O XLLIQLLCWZCATF-UHFFFAOYSA-N 0.000 description 2
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- KWOLFJPFCHCOCG-UHFFFAOYSA-N Acetophenone Chemical compound CC(=O)C1=CC=CC=C1 KWOLFJPFCHCOCG-UHFFFAOYSA-N 0.000 description 2
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 2
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 2
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- BGTOWKSIORTVQH-UHFFFAOYSA-N cyclopentanone Chemical compound O=C1CCCC1 BGTOWKSIORTVQH-UHFFFAOYSA-N 0.000 description 2
- 125000004386 diacrylate group Chemical group 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- ARXJGSRGQADJSQ-UHFFFAOYSA-N 1-methoxypropan-2-ol Chemical compound COCC(C)O ARXJGSRGQADJSQ-UHFFFAOYSA-N 0.000 description 1
- SBASXUCJHJRPEV-UHFFFAOYSA-N 2-(2-methoxyethoxy)ethanol Chemical compound COCCOCCO SBASXUCJHJRPEV-UHFFFAOYSA-N 0.000 description 1
- AZCYBBHXCQYWTO-UHFFFAOYSA-N 2-[(2-chloro-6-fluorophenyl)methoxy]benzaldehyde Chemical compound FC1=CC=CC(Cl)=C1COC1=CC=CC=C1C=O AZCYBBHXCQYWTO-UHFFFAOYSA-N 0.000 description 1
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-UHFFFAOYSA-N 0.000 description 1
- AMIJXNFLZXFHJA-UHFFFAOYSA-N 2-dimethylphosphoryl-1-(2,4,6-trimethylphenyl)ethanone Chemical compound CC1=C(C(=O)CP(C)(C)=O)C(=CC(=C1)C)C AMIJXNFLZXFHJA-UHFFFAOYSA-N 0.000 description 1
- NLGDWWCZQDIASO-UHFFFAOYSA-N 2-hydroxy-1-(7-oxabicyclo[4.1.0]hepta-1,3,5-trien-2-yl)-2-phenylethanone Chemical compound OC(C(=O)c1cccc2Oc12)c1ccccc1 NLGDWWCZQDIASO-UHFFFAOYSA-N 0.000 description 1
- NDAJNMAAXXIADY-UHFFFAOYSA-N 2-methylpropanimidamide Chemical compound CC(C)C(N)=N NDAJNMAAXXIADY-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 229910002567 K2S2O8 Inorganic materials 0.000 description 1
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 1
- 229910004882 Na2S2O8 Inorganic materials 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Natural products P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 1
- LXEKPEMOWBOYRF-UHFFFAOYSA-N [2-[(1-azaniumyl-1-imino-2-methylpropan-2-yl)diazenyl]-2-methylpropanimidoyl]azanium;dichloride Chemical compound Cl.Cl.NC(=N)C(C)(C)N=NC(C)(C)C(N)=N LXEKPEMOWBOYRF-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O ammonium group Chemical group [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 239000000908 ammonium hydroxide Substances 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 108010038083 amyloid fibril protein AS-SAM Proteins 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 235000006708 antioxidants Nutrition 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 229960005070 ascorbic acid Drugs 0.000 description 1
- 235000010323 ascorbic acid Nutrition 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- LBSPZZSGTIBOFG-UHFFFAOYSA-N bis[2-(4,5-dihydro-1h-imidazol-2-yl)propan-2-yl]diazene;dihydrochloride Chemical compound Cl.Cl.N=1CCNC=1C(C)(C)N=NC(C)(C)C1=NCCN1 LBSPZZSGTIBOFG-UHFFFAOYSA-N 0.000 description 1
- 229930188620 butyrolactone Natural products 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- XXJWXESWEXIICW-UHFFFAOYSA-N diethylene glycol monoethyl ether Chemical compound CCOCCOCCO XXJWXESWEXIICW-UHFFFAOYSA-N 0.000 description 1
- 150000002009 diols Chemical class 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000010413 gardening Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- CATSNJVOTSVZJV-UHFFFAOYSA-N heptan-2-one Chemical compound CCCCCC(C)=O CATSNJVOTSVZJV-UHFFFAOYSA-N 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- FAQJJMHZNSSFSM-UHFFFAOYSA-N phenylglyoxylic acid Chemical compound OC(=O)C(=O)C1=CC=CC=C1 FAQJJMHZNSSFSM-UHFFFAOYSA-N 0.000 description 1
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 229920000193 polymethacrylate Polymers 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- FBCQUCJYYPMKRO-UHFFFAOYSA-N prop-2-enyl 2-methylprop-2-enoate Chemical compound CC(=C)C(=O)OCC=C FBCQUCJYYPMKRO-UHFFFAOYSA-N 0.000 description 1
- QTECDUFMBMSHKR-UHFFFAOYSA-N prop-2-enyl prop-2-enoate Chemical compound C=CCOC(=O)C=C QTECDUFMBMSHKR-UHFFFAOYSA-N 0.000 description 1
- LLHKCFNBLRBOGN-UHFFFAOYSA-N propylene glycol methyl ether acetate Chemical compound COCC(C)OC(C)=O LLHKCFNBLRBOGN-UHFFFAOYSA-N 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 229920001059 synthetic polymer Polymers 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
- C08J3/242—Applying crosslinking or accelerating agent onto compounding ingredients such as fillers, reinforcements
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
- C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
- C08J3/075—Macromolecular gels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
- B01J20/26—Synthetic macromolecular compounds
- B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
- B01J20/267—Cross-linked polymers
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
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Definitions
- the present invention relates to a super absorbent polymer exhibiting more improved absorption rate and liquid permeability, as well as having excellent basic absorption performance, and a method for producing the same.
- Super absorbent polymer is a synthetic polymer material capable of absorbing moisture from about 500 to about 1,000 times its own weight, and each manufacturer has denominated it as different names such as SAM (Super Absorbency Material), AGM (Absorbent Gel Material) or the like.
- SAM Super Absorbency Material
- AGM Absorbent Gel Material
- Such super absorbent polymers started to be practically applied in sanitary products, and now they are widely used for preparation of hygiene products such as paper diapers for children or sanitary napkins, water retaining soil products for gardening, water stop materials for the civil engineering and construction, sheets for raising seedling, fresh-keeping agents for food distribution fields, materials for poultice or the like.
- these super absorbent polymers have been widely used in the field of hygienic materials such as diapers or sanitary napkins.
- the super absorbent polymers should exhibit a high absorption performance with respect to moisture, etc., it should not release the absorbed water even in the external pressure, and additionally it should well retain the shape even in a state where the volume is expanded (swelled) by absorbing water, and thereby exhibit excellent liquid permeability.
- the water absorbent polymer needs to have the performance of the fiber material of the diaper.
- the water absorbent polymer should have a high water absorption performance as well as a high absorption rate and a liquid permeability.
- the hydrogel prepared by polymerizing the monomer of the water absorbent polymer.
- the pulverization of the hydrogel is a process required for producing a super absorbent polymer in the form of a powder or a particle, and this process greatly affects the physical properties of the super absorbent polymer.
- Japanese Patent No. 3415036 discloses a preparation method that minimizes damage to hydrogel during pulverization of the hydrogel, in order to reduce extractable contents that can induce a reduction in water absorption capacity.
- the above method can achieve a high absorption performance, but it is insufficient to obtain the absorption rate at the level recently required for diapers.
- the present invention provides a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the super absorbent polymer has the following features: a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g, a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 ( ⁇ 10 -7 cm 3 ⁇ s/g) or more, and T-20 of 180 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20 g of aque
- the present invention provides a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the super absorbent polymer has the following features: a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g, a centrifuge retention capacity (CRC) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 30 minutes of 26 g/g to 34 g/g, a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt%
- FHA fixed height absorption
- the present invention provides a method for producing a super absorbent polymer comprising the steps of: performing crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer containing a first crosslinked polymer and having a gel strength of 10000 Pa or more; performing gel pulverization of the hydrogel polymer so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization; drying, pulverizing and classifying the gel pulverized hydrogel polymer to form a base polymer power; and heat-treating and surface-crosslinking the base polymer powder in the presence of a surface crosslinking agent to form a super absorbent polymer particle.
- a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the super absorbent polymer has the following features: a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g, a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 ( ⁇ 10 -7 cm 3 ⁇ s/g) or more, and T-20 of 180 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20
- FHA fixed height absorption
- the present inventors have found that according to a production method described later, when controlling the polymerization conditions to obtain a hydrogel polymer having a high gel strength, controlling the gel-pulverizing condition thereof so that the gel strength after gel-pulverization is maintained in an appropriate range and then producing a super absorbent polymer through a subsequent process, it is possible to produce and provide a super absorbent polymer having not only excellent basic absorption performance but also greatly improved liquid permeability and absorption rate, thereby completing the present invention.
- the super absorbent polymer of one embodiment can exhibit excellent liquid permeability defined by a relatively high SFC and excellent suction force under pressure such as absorption under pressure defined by high FHA and the like.
- the super absorbent polymer of one embodiment can exhibit an improved absorption rate as defined, for example, by the physical properties such as T-20.
- the super absorbent polymer of one embodiment obtained through such a method can reduce the generation of extractable contents and the deterioration of absorption performance in the course of its production.
- the super absorbent polymer of one embodiment can exhibit more improved absorption rate and liquid permeability, while maintaining excellent basic absorption performance, and can be preferably used for hygienic materials such as diapers having a thinner thickness.
- super absorbent polymer refers to a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent.
- the water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the production of a super absorbent polymer.
- the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Chemical Formula 1: [Chemical Formula 1] R 1 -COOM 1 in Chemical Formula 1,
- the above-described monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, and a monovalent metal salt, a divalent metal salt, an ammonium salt, and an organic amine salt thereof.
- acrylic acid or a salt thereof is used as the water-soluble ethylenically unsaturated monomer, it is advantageous in that a super absorbent polymer having improved absorption property can be obtained.
- the above-mentioned monomer used herein may include at least one selected from the group consisting of an anionic monomer such as maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloyl ethane sulfonic acid, 2-methacryloyl ethane sulfonic acid, 2-(meth)acryloyl propane sulfonic acid, or 2-(meth)acrylamide-2-methylpropane sulfonic acid, and a salt thereof; a nonionic hydrophilic monomer such as (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxypolyethyleneglycol(meth)acrylate, or polyethyleneglycol(meth)acrylate; and an unsaturated monomer containing amino group such as (N,N)-dimethylaminoethyl(meth)
- the water-soluble ethylenically unsaturated monomer may have an acidic group, wherein at least a part of the acidic group is neutralized.
- an alkaline substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like can be used.
- the degree of neutralization of the monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%.
- the range of the degree of neutralization may vary depending on the final physical properties.
- an excessively high degree of neutralization causes the neutralized monomers to be precipitated, and thus polymerization may not readily occur, whereas an excessively low degree of neutralization not only greatly deteriorates the absorption performance of the polymer, but also endows the polymer with hard-to-handle properties, like elastic rubber.
- first crosslinked polymer means that the above-mentioned water-soluble ethylenically unsaturated monomer is subjected to a crosslinking polymerization in the presence of an internal crosslinking agent
- base polymer powder means a substance containing such a first crosslinked polymer
- second crosslinked polymer means a substance in which the first crosslinked polymer is additionally crosslinked via a surface crosslinking agent, whereby the second crosslinked polymer is formed on the base polymer powder.
- the surface crosslinking agent will be described later.
- the super absorbent polymer of one embodiment is excellent in water absorption capacity, absorption rate and liquid permeability, which can be expressed by physical properties such as CRC, FHA, SFC, T-20 or FSR.
- the super absorbent polymer of one embodiment has a centrifuge retention capacity (CRC) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 30 minutes of 26 g/g or more, preferably 26.5 g/g or more, or 27.0 g/g or more. Higher the value of CRC, the more excellent it is.
- the upper limit thereof is not restricted, but as an example, it is 34 g/g or less, 32 g/g or less, 30 g/g or less, or 29.5 g/g or less.
- CRC g / g W 2 g ⁇ W 1 g ⁇ W 0 g / W 0 g in Equation 1,
- the super absorbent polymer of one embodiment may have a fixed height absorption (FHA) (20 cm) of 22.5 g/g or more, preferably 23 g/g or more, 23.5 g/g or more, or 23.7 g/g or more as measured after absorbing the same in a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 1 hour under pressure of 0.3 psi.
- FHA fixed height absorption
- the upper limit thereof is not restricted, but as an example, it may be 29 g/g or less, 27 g/g or less, or 26 g/g or less.
- the FHA may be measured and calculated by the method described in Examples of U.S. Patent No. 7,108,916 .
- Such an FHA can define an excellent suction force under pressure exhibited by the super absorbent polymer of one embodiment.
- the super absorbent polymer of one embodiment includes a base polymer powder that maintains a relatively high gel strength, excellent FHA and superior absorption under pressure as defined thereby.
- the super absorbent polymer of one embodiment has a saline flow conductivity (SFC, 10 -7 cm 3 ⁇ s/g) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 or more, preferably 40 or more, 45 or more, or 47 or more.
- the upper limit of SFC is not restricted, but as an example, it is 150 or less, 140 or less, 130 or less, 100 or less, or 80 or less.
- the saline flow conductivity (SFC) may be measured and calculated according to methods well known to those skilled in the art, for example, the methods disclosed in columns 54 to 59 of U.S. Patent No. 5,562,646 .
- the super absorbent polymer includes a base polymer powder which maintains a high gel strength, and includes a surface crosslinked layer through a surface crosslinking, and thus can exhibit a more improved SFC and excellent liquid permeability defined thereby.
- the super absorbent polymer of one embodiment has T-20 of 180 seconds or less, 170 seconds or less, or 160 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20 g of aqueous solution of sodium chloride and alcohol ethoxylate having 12 to 14 carbon atoms under pressure of 0.3 psi.
- the lower limit of T-20 is not restricted, but as an example, it is 80 seconds or more, 90 seconds or more, 100 seconds or more, or 120 seconds or more.
- T-20 9 g of sodium chloride (0.9 wt %) and 0.1 g of Lorodac (main component: linear alcohol ethoxylate having 12 to 14 carbon atoms, CAS #68439-50-9) (0.01 wt %) are dissolved in 1 L of distilled water to make an aqueous solution, and the T-20 can be calculated and measured with the time required for absorbing 1 g of the super absorbent polymer to 20 g of this aqueous solution under pressure of 0.3 psi. Specific measurement methods of T-20 are described in detail on pages 13 to 18 of European Patent Publication No. 2,535,027 .
- the super absorbent polymer of one embodiment can include a base polymer powder having a large surface area by optimizing the gel pulverizing conditions of the hydrogel polymer in its production process. Thereby, the super absorbent polymer can exhibit an improved absorption rate than previously known.
- the super absorbent polymer of one embodiment has the free swell rate (FSR) of 0.25 g/g/s or more, preferably 0.27 g/g/s or more, 0.28 g/g/s or more, or 0.29 g/g/s or more, when 1 g of the super absorbent polymer absorbs 20 g of a 0.9 wt% aqueous sodium chloride solution.
- FSR free swell rate
- the upper limit of the FSR is not restricted, but as an example, it is 0.40 g/g/s or less, 0.39 g/g/s or less, 0.38 g/g/s or less, 0.37 g/g/s or less, or 0.36 g/g/s or less.
- This FSR range can also define the high absorption rate exhibited by the super absorbent polymer of one embodiment.
- the first crosslinked polymer included in the base polymer powder may be a polymer in which the monomer is crosslinked in the presence of a polyolpoly(meth)acrylate-based first internal crosslinking agent selected from the group consisting of trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycoldi(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentacrylate, g
- the super absorbent polymer of one embodiment includes a base polymer powder that maintains a high gel strength even after carrying out gel-pulverization, pulverization or the like, and thereby superior liquid permeability and absorption under pressure can be exhibited.
- the super absorbent polymer of one embodiment described above may have a particle diameter of 150 to 850 ⁇ m. More specifically, at least 95% by weight of the base polymer powder and the super absorbent polymer containing the same may have a particle diameter of 150 to 850 ⁇ m and a fine powder having a particle diameter of less than 150 ⁇ m may be less than 3% by weight.
- the super absorbent polymer satisfying the above-mentioned various properties of the embodiment can be produced by a specific production method in which the hydrogel polymerization conditions are controlled to obtain a hydrogel polymer exhibiting higher gel strength, and then the gel pulverization conditions and the like are controlled to maintain the gel strength after pulverization at a constant level.
- Such production method may include the steps of: performing crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer containing a first crosslinked polymer and having a gel strength pf 10000 Pa or more; performing gel pulverization of the hydrogel polymer so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization; drying, pulverizing and classifying the gel pulverized hydrogel polymer to form a base polymer power; and heat-treating and surface-crosslinking the base polymer powder in the presence of a surface crosslinking agent to form a super absorbent polymer particle.
- the production method of another embodiment includes a step of forming a hydrogel polymer by crosslinking. Specifically, this is a step of performing thermal polymerization or photo-polymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator in the presence of an internal crosslinking agent to form a hydrogel polymer.
- the water-soluble ethylenically unsaturated monomer contained in the monomer composition is the same as described above.
- the monomer composition may include a polymerization initiator generally used in the production of a super absorbent polymer.
- a polymerization initiator generally used in the production of a super absorbent polymer.
- a thermal polymerization initiator, a photo-polymerization initiator or the like may be used depending on the polymerization method.
- a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, and thus, a thermal polymerization initiator may further be included.
- the photo-polymerization initiator used herein may include, for example, one or more compounds selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine and ⁇ -aminoketone.
- benzoin ether dialkyl acetophenone
- hydroxyl alkyl ketone hydroxyl alkyl ketone
- phenyl glyoxylate benzyl dimethyl ketal
- acyl phosphine a commonly used lucyrin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide may be used.
- thermal polymerization initiator one or more compounds selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used.
- a persulfate-based initiator may include sodium persulfate (Na 2 S 2 O 8 ), potassium persulfate (K 2 S 2 O 8 ), ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), and the like.
- examples of the azo-based initiator may include 2,2-azobis(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 4,4-azobis-(4-cyanovaleric acid) or the like. More various thermal polymerization initiators are well disclosed in " Principle of Polymerization” written by Odian, (Wiley, 1981), p 203 , the content of which is incorporated herein by reference.
- the polymerization initiator may be included in a concentration of about 0.001 to 1% by weight based on the monomer composition. That is, when the concentration of the polymerization initiator is too low, the polymerization rate may become slow and a large amount of residual monomer may be extracted in the final product, which is not preferable. On the other hand, when the concentration of the polymerization initiator is too high, the polymer chains constituting the network become short, and thus the extractable contents are increased and physical properties of the polymer may deteriorate such as a reduction in absorption under pressure.
- the monomer composition may include a crosslinking agent ("internal crosslinking agent”) to improve physical properties of the polymer by polymerization of the water-soluble ethylenically unsaturated monomer.
- the crosslinking agent is used for internal crosslinking of the hydrogel polymer, and is used separately from a surface crosslinking agent described below.
- the above-mentioned two or more internal crosslinking agents for example, the polyol poly(meth)acrylate first internal crosslinking agent and the allyl(meth)acrylate-based second internal crosslinking agent can be used together to obtain a hydrogel polymer having a higher gel strength, for example, a gel strength of 10000 Pa or more, or 11000 Pa or more, or 120000 Pa or more, and but not particularly limited thereto, 50000 Pa or less, or 40,000 Pa or less, or 38,000 Pa or less.
- the first internal crosslinking agent at least one selected from the group consisting of trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene di(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentacrylate, glycerin tri(meth)acrylate, and pentaerythritol tetraacrylate may be used, and as the second internal crosslinking agent, allyl(meth)acrylate, allylacrylate, ally
- the first internal crosslinking agent may be added in an amount of 0.4 to 1 part by weight, or 0.5 to 0.9 parts by weight, or 0.6 to 0.8 parts by weight, based on 100 parts by weight of the entire monomer composition including the internal crosslinking agent, the monomer and the like.
- the second internal crosslinking agent may be added in an amount of 0.008 to 0.5 parts by weight, or 0.01 to 0.1 parts by weight, or 0.01 to 0.05 parts by weight, based on 100 parts by weight of the entire monomer composition.
- the monomer composition may further include an additive such as a thickener, a plasticizer, a preservation stabilizer, an antioxidant, etc., if necessary.
- an additive such as a thickener, a plasticizer, a preservation stabilizer, an antioxidant, etc., if necessary.
- Such monomer composition can be prepared in the form of a solution in which raw materials such as the above-described monomer, polymerization initiator, internal crosslinking agent, etc. are dissolved in a solvent.
- any usable solvent can be used without limitation in the constitution as long as it can dissolve the above-mentioned raw materials.
- the solvent may include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethylether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N,N-dimethylacetamide, or a mixture thereof.
- the formation of the hydrogel polymer through polymerization of the monomer composition may be performed by a general polymerization method, and the process is not particularly limited.
- the polymerization method are largely classified into a thermal polymerization and a photo-polymerization according to the type of the polymerization energy source, and the thermal polymerization may be carried out in a reactor like a kneader equipped with agitating spindles and the photo-polymerization may be carried out in a reactor equipped with a movable conveyor belt.
- the monomer composition is injected into a reactor like a kneader equipped with the agitating spindles, and thermal polymerization is performed by providing hot air thereto or heating the reactor, thereby obtaining the hydrogel polymer.
- the hydrogel polymer which is discharged from the outlet of the reactor according to the type of agitating spindles equipped in the reactor, may be obtained as particles with a size of centimeters or millimeters.
- the hydrogel polymer may be obtained in various forms according to the concentration of the monomer composition injected thereto, the injection speed, or the like, and the hydrogel polymer having a (weight average) particle diameter of 2 to 50 mm may be generally obtained.
- a sheet-shaped hydrogel polymer may be obtained.
- the thickness of the sheet may vary depending on the concentration of the monomer composition injected thereto and the injection speed, and the polymer sheet is preferably controlled to have typically a thickness of 0.5 to 10 cm in order to secure the production speed or the like while enabling a uniform polymerization of the entire sheet.
- the hydrogel polymer obtained by the above-mentioned method may have a water content of 38 to 60% by weight or 40 to 55% by weight.
- the "water content” as used herein means a weight occupied by moisture with respect to a total weight of the hydrogel polymer, which may be the value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer.
- the water content can be defined as a value calculated by measuring the weight loss due to evaporation of moisture in the polymer in the drying process by raising the temperature of the polymer through infrared heating.
- the drying conditions may be determined as follows: the drying temperature is increased from room temperature to about 180°C and then the temperature may be maintained at 180°C, and the total drying time may be set to 20 minutes, including 5 minutes for the temperature rising step.
- the hydrogel polymer is introduced into a gel pulverizer in the state where the water content has been adjusted.
- the gel pulverization conditions described below are adjusted, not only the high gel strength range before gel pulverization can be more easily achieved, the gel strength after gel pulverization can be maintained at 35% to 95%, or 50% to 90%, or 60% to 88% of the gel strength before the pulverization.
- the inner surface area of the base polymer powder and the super absorbent polymer containing the same is widened, whereby the super absorbent polymer exhibits excellent absorption rate, and also the base polymer powder and the super absorbent polymer can maintain high strength and so exhibit excellent liquid permeability and the like.
- the hydrogel polymer with controlled water content is gel-pulverized.
- Such gel pulverization can be carried out so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization.
- the gel strength after gel pulverization may be from 5000Pa to 30000Pa, or from 10000Pa to 28000Pa.
- the pulverizing device used in the pulverization step is not limited in its constitution, but specific examples thereof may include any one selected from the group consisting of a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper and a disc cutter. However, it is not limited to the above-described example.
- the gel strength range after the gel pulverization described above can be achieved by controlling the gel pulverization conditions.
- the gel pulverization can be carried out inside a pulverizer including an extruder equipped with a perforated plate such as a screw extruder.
- a perforated plate such as a screw extruder.
- a plurality of holes formed in the perforated plate may have a diameter of 9 to 18 mm, or 10 to 15 mm, whereby the gel pulverization can be carried out by pushing the hydrogel polymer through such a perforated plate and an extruder.
- the hydrogel polymer can maintain an adequate level of gel strength even after gel pulverization, and the gel pulverization is effectively carried out so that the polymer after pulverization can have a large surface area.
- the surface area of the pulverized hydrogel polymer is remarkably increased.
- the percentage of the number of sheared particles is 0.40 or more and 0.95 or less.
- the "sheared particle” means a particle having three or more concave portions or holes with a depth of 10 ⁇ m or more observed on the pulverized hydrogel polymer particle, and the "number ratio of the sheared particles” means the number of the sheared particles relative to the total number of the hydrogel polymer particles.
- the sheared particles are produced and the surface area is widened, so that the physical properties of the super absorbent polymer can be more improved and the super absorbent polymer satisfying the various physical properties of one embodiment can be produced more effectively.
- the pulverization of the hydrogel polymer may be performed such that the hydrogel polymer has a particle diameter of 0.1 mm to 10 mm. That is, in order to increase the drying efficiency, the hydrogel polymer is preferably pulverized into particles with a size of 10 mm or less. However, since a phenomenon of agglomeration between particles may occur during excessive pulverization, the hydrogel polymer is preferably pulverized into particles with a size of 0.1 mm or more.
- the hydrogel polymer can be dried.
- the drying can be carried out at a temperature of 120 to 250°C, preferably 140 to 200°C, more preferably 150 to 190°C.
- the drying temperature can be defined as the temperature of the heating medium provided thereto for drying, or the internal temperature of the drying reactor including the heating medium and the polymer during the drying process. If the drying temperature is low, and therefore the drying time becomes long, the efficiency of the process may be deteriorated. In order to prevent this problem, the drying temperature is preferably 120°C or higher.
- the drying temperature is preferably 250°C or lower.
- the drying time in the drying step is not particularly limited, but it may be controlled to 20 to 90 minutes at the above drying temperature, in consideration of the process efficiency and the physical properties of the polymer.
- the drying can be carried out using a conventional medium, and for example, the drying may be carried out by the methods of subjecting the pulverized hydrogel polymer to hot air supply, infrared irradiation, microwave irradiation, ultraviolet irradiation or the like.
- the drying is preferably carried out so that the dried polymer has a water content of about 0.1% to 10% by weight. That is, if the water content of the dried polymer is less than 0.1% by weight, production costs may be increased due to excessive drying and degradation of the crosslinked polymer may occur, which is not desirable. In addition, if the water content of the polymer is more than 10% by weight, defects may occur in a subsequent process, which is not desirable.
- the dried polymer can be pulverized.
- the particle diameter and surface area of the pulverized polymer can be controlled within an appropriate range.
- the pulverization can be carried out such that the pulverized polymer has a particle diameter of 150 to 850 ⁇ m.
- Examples of the pulverizing device that can be used herein include a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jog mill or the like.
- the step of selectively classifying particles having a particle diameter of 150 to 850 ⁇ m in the polymer particles obtained through the above-mentioned pulverization step may be further performed.
- polymer particles fine powder having a particle diameter of less than 150 ⁇ m can be granulated with a solvent (for example, aqueous solvent such as water) usable in the crosslinking polymerization step to prepare a fine powder re-granulated body.
- a solvent for example, aqueous solvent such as water
- the fine powder re-granulated body may be added and mixed to the super absorbent polymer before the drying, for example, to the super absorbent polymer just before or just after the gel pulverization step, and between the drying step.
- the fine powder re-granulated body may be mixed in an amount of 10 to 30 parts by weight, or 15 to 28 parts by weight based on 100 parts by weight of the hydrogel polymer before drying. Due to the addition of such fine powder re-granulated body, the internal surface area of the base polymer powder and the super absorbent polymer can be more widened and the super absorbent polymer can exhibit a more enhanced absorption rate. In addition, the strength of the base polymer powder and the super absorbent polymer is controlled to an appropriate range by introducing the fine powder re-granulated body within the above-mentioned content range, and thus various physical properties of one embodiment can be achieved more effectively.
- the base polymer powder after the base polymer powder is produced through the classification step described above, the base polymer powder can be subjected to heat treatment and surface crosslinking in the presence of a surface crosslinking agent to form super absorbent polymer particles.
- the surface crosslinking induces a crosslinking reaction on the surface of the base polymer powder in the presence of a second crosslinking agent (surface crosslinking agent).
- a surface modified layer is formed on the surface of the pulverized polymer particles.
- the surface crosslinking may be performed by a method of mixing a solution containing a second crosslinking agent (surface crosslinking agent) with the base polymer powder followed by a crosslinking reaction.
- a second crosslinking agent surface crosslinking agent
- the surface crosslinking agent is a compound capable of reacting with a functional group of the polymer, and may be an alkylene carbonate-based compound or a polyhydric alcohol-based compound.
- An alkylene carbonate having 2 to 5 carbon atoms is preferable. More preferably, ethylene carbonate can be used as the surface crosslinking agent.
- silica, clay or the like can be further used.
- an acidic compound, a polymer, or the like can be further added, if necessary.
- the content of the surface crosslinking agent may be appropriately controlled according to the kind of crosslinking agent, reaction conditions, etc., and may be preferably adjusted to 0.001 to 5 parts by weight based on 100 parts by weight of the base polymer powder. If the content of the surface crosslinking agent is excessively low, the surface modification may not be properly performed, and the physical properties of the final polymer may be deteriorated. Conversely, if an excess amount of the surface crosslinking agent is used, the basic absorption capacity of the polymer may rather decrease due to excessive surface crosslinking reaction, which is not preferable.
- the surface crosslinking step may be performed by a conventional method such as a method in which the surface crosslinking solution containing the surface crosslinking agent and the base polymer powder are added to a reaction vessel and mixed, a method in which the surface crosslinking solution containing the surface crosslinking agent is sprayed onto the base polymer powder, a method in which the base polymer powder and the surface crosslinking solution are continuously supplied in a continuously operating mixer and mixed, and the like.
- a conventional method such as a method in which the surface crosslinking solution containing the surface crosslinking agent and the base polymer powder are added to a reaction vessel and mixed, a method in which the surface crosslinking solution containing the surface crosslinking agent is sprayed onto the base polymer powder, a method in which the base polymer powder and the surface crosslinking solution are continuously supplied in a continuously operating mixer and mixed, and the like.
- water when adding the surface crosslinking agent, water may be further added.
- adding the surface crosslinking agent and water together may induce uniform dispersion of the surface crosslinking agent, prevent the aggregation phenomenon of the base polymer powder, and further optimize the penetration depth of the surface crosslinking agent to the base polymer powder.
- the content of water to be added together with the surface crosslinking agent may be adjusted to 0.5 to 10 parts by weight based on 100 parts by weight of the base polymer powder.
- the surface crosslinking step may be proceeded at a temperature of 100 to 250° C. Further, the surface crosslinking can be proceeded for 1 minute to 120 minutes, preferably 1 minute to 100 minutes, more preferably 10 minutes to 80 minutes. That is, in order to prevent the polymer particles from being damaged to thereby decrease their physical properties during excessive reaction while inducing the minimum surface cross-linking reaction, the surface crosslinking step may be carried out under the above-mentioned conditions.
- the super absorbent polymer according to the present invention can exhibit more improved absorption rate and liquid permeability, while maintaining excellent basic absorption performance, and thus is preferably used for hygienic materials such as diapers having a thinner thickness.
- a continuous manufacturing apparatus comprising a polymerization step, a hydrogel pulverizing step, a drying step, a pulverization step, a classification step, a surface cross-linking step, a cooling step, a classification step, and a transport step connecting respective steps can be used.
- the hydrogel was cut to have an average size of about 300 mm or less, and then introduced into a pulverizer (equipped with a perforated plate including a plurality of holes having a diameter of 11 mm) together with a fine powder re-granulated body as shown in Table 1 below and pulverized under the respective conditions.
- a pulverizer equipped with a perforated plate including a plurality of holes having a diameter of 11 mm
- the fine powder re-granulated body used the fine powder re-granulated body prepared in step 4 below, and the input ratio is shown in Table 1 as 20 weight % relative to the hydrogel.
- the hydrogel pulverized in step 2 were dried in an oven capable of shifting airflow up and down.
- the hydrogel was uniformly dried by flowing hot air at 180°C from the bottom to the top for 15 minutes and from the top to the bottom for 15 minutes, so that the dried product had a water content of about 2% or less.
- step 3 The polymer dried in step 3 was pulverized using a pulverizer and classified to obtain a base polymer having a size of 150 to 850 ⁇ m. On the other hand, through the above classification, the polymer particles having a particle size of less than 150 ⁇ m was granulated with water and used for the fine powder re-granulated body of step 2 described above.
- step 4 100 parts by weight of the base polymer prepared in step 4 was mixed with a crosslinking agent solution containing 4 parts by weight of water and 1 part by weight of ethylene carbonate and then subjected to a surface crosslinking reaction at 180°C for 40 minutes. Then, the obtained product was cooled and classified to obtain a surface-crosslinked super absorbent polymer having a particle diameter of 150 to 850 ⁇ m.
- a super absorbent polymer was prepared in the same manner as in Example 1, except that the content range of the internal crosslinking agent, the hole diameter of the perforated plate provided in the gel pulverizer, the water content of the hydrogel and the input ratio of the fine powder re-granulated body were changed as shown in Table 1 below.
- a hydrogel sample to be measured (a hydrogel sheet before gel pulverization and a hydrogel after gel pulverization) was prepared to have a diameter of about 2.5 cm and a thickness of about 2 to 5 mm.
- the prepared sample was loaded on a microbalance, and an appropriate amount of distilled water was evenly sprayed using a sprayer (At this time, the initial water content of the hydrogel was measured in advance (water content measuring instrument condition: 180°C, 40 minutes), and the amount of water required to match the initial water content was calculated).
- water content measuring instrument condition: 180°C, 40 minutes water content measuring instrument condition
- a hydrogel sample with controlled water content was loaded between two plates of the rheometer (ARES-G2), and the gap between the two plates was properly adjusted by pressing the plates with a force of 3 N so that the sample was contacted at the front face of the plate. Rest time was given for 5 minutes to stabilize the sample.
- a strain in the linear viscoelastic regime section where the storage modulus (G') and the loss modulus (G") were constant was found while increasing the strain at a frequency of 10 rad/s.
- the viscoelasticity (G', G) was measured for 60 seconds at a constant frequency (10 rad/s). After three or more measurements, the average value of G' was calculated as the gel strength (G').
- Comparative Example 1 the water content of the hydrogel before gel pulverization is excessively high, so that the hydrogel before and after gel pulverization shows a low gel strength. Even in Comparative Example 4, the content of the internal crosslinking agent is excessively low, so that the hydrogel before gel pulverization shows a low gel strength. Further, in Comparative Examples 2 and 3, the hole diameter of the perforated plate of the gel pulverizer is not maintained at an appropriate level, and so the gel strength after the gel pulverization deviates from the appropriate range.
- the centrifuge retention capacity(CRC) by water absorption capacity under a non-loading condition was measured for the super absorbent polymers of Examples and Comparative Examples in accordance with EDANA (European Disposables and Nonwovens Association) recommended test method No. WSP 241.3.
- Wo g, about 0.2 g
- the bag was immersed in a physiological saline solution composed of 0.9 wt% aqueous sodium chloride solution at room temperature. After 30 minutes, water was removed from the bag by centrifugation at 250 G for 3 minutes, and the weight W 2 (g) of the bag was then measured.
- CRC (g/g) was calculated according to the following Equation 1, thereby confirming the centrifuge retention capacity.
- CRC g / g W 2 g ⁇ W 1 g ⁇ W 0 g / W 0 g
- the physiological saline flow conductivity (SFC) was measured and calculated according to the method disclosed in columns 54 to 59 of U.S. Patent No. 5,562,646 .
- T-20 9 g of sodium chloride and 0.1 g of Lorodac (main component: linear alcohol ethoxylate having 12 to 14 carbon atoms, CAS #68439-50-9) were dissolved in 1 L of distilled water to make an aqueous solution, and the T-20 was calculated and measured with the time required for absorbing 1 g of the super absorbent polymer to 20 g of this aqueous solution under pressure of 0.3 psi. Specific measurement methods of T-20 were described in detail on pages 13 to 18 of European Patent Publication No. 2535027 .
- the FSR of the base polymer powder or the super absorbent polymer was measured and calculated by using those classified into #30 to #50 (for example, those having a particle diameter of 300 to 600 ⁇ m) according to the method disclosed on pages 22 to 23 of European Patent Publication No. 2535027 .
- the measurement was performed after absorbing the super absorbent polymer to a physiological saline solution (0.9 wt% aqueous sodium chloride solution) under pressure of 0.3 psi, which was measured and calculated as a fixed height absorption (FHA) (20 cm).
- FHA fixed height absorption
Abstract
Description
- This application claims priority to and the benefit of Korean Patent Application No.
10-2016-0178407 filed on December 23, 2016 - The present invention relates to a super absorbent polymer exhibiting more improved absorption rate and liquid permeability, as well as having excellent basic absorption performance, and a method for producing the same.
- Super absorbent polymer (SAP) is a synthetic polymer material capable of absorbing moisture from about 500 to about 1,000 times its own weight, and each manufacturer has denominated it as different names such as SAM (Super Absorbency Material), AGM (Absorbent Gel Material) or the like. Such super absorbent polymers started to be practically applied in sanitary products, and now they are widely used for preparation of hygiene products such as paper diapers for children or sanitary napkins, water retaining soil products for gardening, water stop materials for the civil engineering and construction, sheets for raising seedling, fresh-keeping agents for food distribution fields, materials for poultice or the like.
- In most cases, these super absorbent polymers have been widely used in the field of hygienic materials such as diapers or sanitary napkins. For these applications, the super absorbent polymers should exhibit a high absorption performance with respect to moisture, etc., it should not release the absorbed water even in the external pressure, and additionally it should well retain the shape even in a state where the volume is expanded (swelled) by absorbing water, and thereby exhibit excellent liquid permeability.
- In recent years, as the demand for a thin diaper increases, the proportion of the absorbent polymer in the diaper tends to increase. Therefore, the water absorbent polymer needs to have the performance of the fiber material of the diaper. For this, the water absorbent polymer should have a high water absorption performance as well as a high absorption rate and a liquid permeability.
- In the process of producing the water absorbent polymer, it is generally necessary to pulverize the hydrogel prepared by polymerizing the monomer of the water absorbent polymer. The pulverization of the hydrogel is a process required for producing a super absorbent polymer in the form of a powder or a particle, and this process greatly affects the physical properties of the super absorbent polymer.
- In this regard, various studies have been undertaken. As an example, Japanese Patent No.
3415036 - As another example, International Application
PCT-JP2011-058829 - For these reasons, there is a continuing need to develop a technique capable of providing a super absorbent polymer having more improved water absorption capacity, absorption rate and liquid permeability while maintaining excellent basic absorption performance.
- It is one object of the present invention to provide a super absorbent polymer exhibiting more improved absorption rate and liquid permeability, as well as having excellent basic absorption performance, and a method for producing the same.
- The present invention provides a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the super absorbent polymer has the following features: a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g, a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 (·10-7 cm3·s/g) or more, and T-20 of 180 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20 g of aqueous solution of 0.9 wt% sodium chloride and 0.01 wt% alcohol ethoxylate having 12 to 14 carbon atoms under pressure of 0.3 psi.
- As another example of the super absorbent polymer, the present invention provides a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the super absorbent polymer has the following features: a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g, a centrifuge retention capacity (CRC) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 30 minutes of 26 g/g to 34 g/g, a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 (·10-7 cm3·s/g) or more, and a free swell rate (FSR) of 0.25 g/g/s to 0.40 g/g/s when 1 g of the super absorbent polymer absorbs 20 g of a 0.9 wt% aqueous sodium chloride solution.
- In addition, the present invention provides a method for producing a super absorbent polymer comprising the steps of: performing crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer containing a first crosslinked polymer and having a gel strength of 10000 Pa or more; performing gel pulverization of the hydrogel polymer so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization; drying, pulverizing and classifying the gel pulverized hydrogel polymer to form a base polymer power; and heat-treating and surface-crosslinking the base polymer powder in the presence of a surface crosslinking agent to form a super absorbent polymer particle.
- Hereinafter, a super absorbent polymer according to a specific embodiment of the present invention and a production method thereof will be described in detail. However, this is merely presented as an example of the present invention, and will be apparent to those skilled in the art that the scope of the present invention is not limited to these embodiments, and various modifications can be made to the embodiments within the scope of the present invention.
- In addition, unless stated otherwise throughout this specification, the term "comprises" or "contains" refers to including any constituent element (or constituent component) without particular limitation, and it cannot be interpreted as a meaning of excluding an addition of other constituent element (or constituent component).
- According to one embodiment of the invention, there is provided a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the super absorbent polymer has the following features: a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g, a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 (·10-7 cm3·s/g) or more, and T-20 of 180 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20 g of aqueous solution of 0.9 wt% sodium chloride and 0.01 wt% alcohol ethoxylate having 12 to 14 carbon atoms under pressure of 0.3 psi.
- As a result of continuous studies and experiments, the present inventors have found that according to a production method described later, when controlling the polymerization conditions to obtain a hydrogel polymer having a high gel strength, controlling the gel-pulverizing condition thereof so that the gel strength after gel-pulverization is maintained in an appropriate range and then producing a super absorbent polymer through a subsequent process, it is possible to produce and provide a super absorbent polymer having not only excellent basic absorption performance but also greatly improved liquid permeability and absorption rate, thereby completing the present invention.
- That is, by basically obtaining a hydrogel polymer having a high gel strength and adjusting the gel pulverizing condition so that the gel strength of the hydrogel polymer can be maintained at a certain level or more even after the gel pulverization, it is possible to provide a base polymer powder and a super absorbent polymer exhibiting a relatively high gel strength. Accordingly, the super absorbent polymer of one embodiment can exhibit excellent liquid permeability defined by a relatively high SFC and excellent suction force under pressure such as absorption under pressure defined by high FHA and the like.
- Moreover, it has been found that since the base polymer powder and the super absorbent polymer containing a large number of pores and having a large surface area can be obtained by the progress of the gel pulverization, the super absorbent polymer of one embodiment can exhibit an improved absorption rate as defined, for example, by the physical properties such as T-20.
- In addition, after basically obtaining a hydrogel polymer having a high gel strength, as the gel pulverization condition is controlled so that the gel strength after pulverization is maintained at a certain level or more, the super absorbent polymer of one embodiment obtained through such a method can reduce the generation of extractable contents and the deterioration of absorption performance in the course of its production.
- Therefore, the super absorbent polymer of one embodiment can exhibit more improved absorption rate and liquid permeability, while maintaining excellent basic absorption performance, and can be preferably used for hygienic materials such as diapers having a thinner thickness.
- Hereinafter, the super absorbent polymer of one embodiment will be described in more detail.
- Further, the term "super absorbent polymer" as used herein refers to a super absorbent polymer comprising: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent.
- The water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the production of a super absorbent polymer. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Chemical Formula 1:
[Chemical Formula 1] R1-COOM1
in Chemical Formula 1, - R1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond, and
- M1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.
- Preferably, the above-described monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, and a monovalent metal salt, a divalent metal salt, an ammonium salt, and an organic amine salt thereof. When acrylic acid or a salt thereof is used as the water-soluble ethylenically unsaturated monomer, it is advantageous in that a super absorbent polymer having improved absorption property can be obtained. In addition, the above-mentioned monomer used herein may include at least one selected from the group consisting of an anionic monomer such as maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloyl ethane sulfonic acid, 2-methacryloyl ethane sulfonic acid, 2-(meth)acryloyl propane sulfonic acid, or 2-(meth)acrylamide-2-methylpropane sulfonic acid, and a salt thereof; a nonionic hydrophilic monomer such as (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxypolyethyleneglycol(meth)acrylate, or polyethyleneglycol(meth)acrylate; and an unsaturated monomer containing amino group such as (N,N)-dimethylaminoethyl(meth)acrylate or (N,N)-dimethylaminopropyl(meth)acrylamide, and a quaternary compound thereof.
- Here, the water-soluble ethylenically unsaturated monomer may have an acidic group, wherein at least a part of the acidic group is neutralized. Preferably, those in which the monomer is partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like can be used.
- In this case, the degree of neutralization of the monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization may vary depending on the final physical properties. However, an excessively high degree of neutralization causes the neutralized monomers to be precipitated, and thus polymerization may not readily occur, whereas an excessively low degree of neutralization not only greatly deteriorates the absorption performance of the polymer, but also endows the polymer with hard-to-handle properties, like elastic rubber.
- The "first crosslinked polymer" means that the above-mentioned water-soluble ethylenically unsaturated monomer is subjected to a crosslinking polymerization in the presence of an internal crosslinking agent, and the "base polymer powder" means a substance containing such a first crosslinked polymer. In addition, the "second crosslinked polymer" means a substance in which the first crosslinked polymer is additionally crosslinked via a surface crosslinking agent, whereby the second crosslinked polymer is formed on the base polymer powder. The surface crosslinking agent will be described later.
- The super absorbent polymer of one embodiment is excellent in water absorption capacity, absorption rate and liquid permeability, which can be expressed by physical properties such as CRC, FHA, SFC, T-20 or FSR.
- Specifically, the super absorbent polymer of one embodiment has a centrifuge retention capacity (CRC) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 30 minutes of 26 g/g or more, preferably 26.5 g/g or more, or 27.0 g/g or more. Higher the value of CRC, the more excellent it is. Thus, the upper limit thereof is not restricted, but as an example, it is 34 g/g or less, 32 g/g or less, 30 g/g or less, or 29.5 g/g or less. The centrifuge retention capacity (CRC) for a physiological saline can be calculated by the following Equation 1 after absorbing the super absorbent polymer to a physiological saline solution over 30 minutes:
- W0(g) is an initial weight(g) of the super absorbent polymer,
- W1(g) is a weight of bag measured after impregnating a nonwoven fabric bag not containing a super absorbent polymer in a physiological saline solution at room temperature for 30 minutes and then dehydrating the same by using a centrifuge at 250 G for 3 minutes, and
- W2(g) is a weight of bag measured after impregnating a nonwoven fabric bag containing a super absorbent polymer in physiological saline at room temperature for 30 minutes and then dehydrating the same by using a centrifuge at 250 G for 3 minutes.
- Moreover, the super absorbent polymer of one embodiment may have a fixed height absorption (FHA) (20 cm) of 22.5 g/g or more, preferably 23 g/g or more, 23.5 g/g or more, or 23.7 g/g or more as measured after absorbing the same in a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 1 hour under pressure of 0.3 psi. The upper limit thereof is not restricted, but as an example, it may be 29 g/g or less, 27 g/g or less, or 26 g/g or less. The FHA may be measured and calculated by the method described in Examples of
U.S. Patent No. 7,108,916 . - Such an FHA can define an excellent suction force under pressure exhibited by the super absorbent polymer of one embodiment. As the super absorbent polymer of one embodiment includes a base polymer powder that maintains a relatively high gel strength, excellent FHA and superior absorption under pressure as defined thereby.
- In addition, the super absorbent polymer of one embodiment has a saline flow conductivity (SFC, 10-7 cm3·s/g) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 or more, preferably 40 or more, 45 or more, or 47 or more. The upper limit of SFC is not restricted, but as an example, it is 150 or less, 140 or less, 130 or less, 100 or less, or 80 or less. The saline flow conductivity (SFC) may be measured and calculated according to methods well known to those skilled in the art, for example, the methods disclosed in columns 54 to 59 of
U.S. Patent No. 5,562,646 . - The super absorbent polymer includes a base polymer powder which maintains a high gel strength, and includes a surface crosslinked layer through a surface crosslinking, and thus can exhibit a more improved SFC and excellent liquid permeability defined thereby.
- Further, the super absorbent polymer of one embodiment has T-20 of 180 seconds or less, 170 seconds or less, or 160 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20 g of aqueous solution of sodium chloride and alcohol ethoxylate having 12 to 14 carbon atoms under pressure of 0.3 psi. The lower limit of T-20 is not restricted, but as an example, it is 80 seconds or more, 90 seconds or more, 100 seconds or more, or 120 seconds or more. 9 g of sodium chloride (0.9 wt %) and 0.1 g of Lorodac (main component: linear alcohol ethoxylate having 12 to 14 carbon atoms, CAS #68439-50-9) (0.01 wt %) are dissolved in 1 L of distilled water to make an aqueous solution, and the T-20 can be calculated and measured with the time required for absorbing 1 g of the super absorbent polymer to 20 g of this aqueous solution under pressure of 0.3 psi. Specific measurement methods of T-20 are described in detail on pages 13 to 18 of European Patent Publication No.
2,535,027 . - The super absorbent polymer of one embodiment can include a base polymer powder having a large surface area by optimizing the gel pulverizing conditions of the hydrogel polymer in its production process. Thereby, the super absorbent polymer can exhibit an improved absorption rate than previously known.
- Further, the super absorbent polymer of one embodiment has the free swell rate (FSR) of 0.25 g/g/s or more, preferably 0.27 g/g/s or more, 0.28 g/g/s or more, or 0.29 g/g/s or more, when 1 g of the super absorbent polymer absorbs 20 g of a 0.9 wt% aqueous sodium chloride solution. The upper limit of the FSR is not restricted, but as an example, it is 0.40 g/g/s or less, 0.39 g/g/s or less, 0.38 g/g/s or less, 0.37 g/g/s or less, or 0.36 g/g/s or less.
- This FSR range can also define the high absorption rate exhibited by the super absorbent polymer of one embodiment.
- Meanwhile, in the super absorbent polymer of the one embodiment described above, the first crosslinked polymer included in the base polymer powder may be a polymer in which the monomer is crosslinked in the presence of a polyolpoly(meth)acrylate-based first internal crosslinking agent selected from the group consisting of trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycoldi(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentacrylate, glycerin tri(meth)acrylate, and pentaerythritol tetraacrylate; and an allyl(meth)acrylate-based second crosslinking agent. By applying these two or more specific internal crosslinking agents, the super absorbent polymer of one embodiment includes a base polymer powder that maintains a high gel strength even after carrying out gel-pulverization, pulverization or the like, and thereby superior liquid permeability and absorption under pressure can be exhibited.
- The super absorbent polymer of one embodiment described above may have a particle diameter of 150 to 850 µm. More specifically, at least 95% by weight of the base polymer powder and the super absorbent polymer containing the same may have a particle diameter of 150 to 850 µm and a fine powder having a particle diameter of less than 150 µm may be less than 3% by weight.
- Meanwhile, the super absorbent polymer satisfying the above-mentioned various properties of the embodiment can be produced by a specific production method in which the hydrogel polymerization conditions are controlled to obtain a hydrogel polymer exhibiting higher gel strength, and then the gel pulverization conditions and the like are controlled to maintain the gel strength after pulverization at a constant level.
- According to another embodiment of the present invention, there is provided a process for producing the above-mentioned super absorbent polymer. Such production method may include the steps of: performing crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer containing a first crosslinked polymer and having a gel strength pf 10000 Pa or more; performing gel pulverization of the hydrogel polymer so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization; drying, pulverizing and classifying the gel pulverized hydrogel polymer to form a base polymer power; and heat-treating and surface-crosslinking the base polymer powder in the presence of a surface crosslinking agent to form a super absorbent polymer particle.
- Hereinafter, the above production method will be described in detail for each step.
- First, the production method of another embodiment includes a step of forming a hydrogel polymer by crosslinking. Specifically, this is a step of performing thermal polymerization or photo-polymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator in the presence of an internal crosslinking agent to form a hydrogel polymer.
- The water-soluble ethylenically unsaturated monomer contained in the monomer composition is the same as described above.
- In addition, the monomer composition may include a polymerization initiator generally used in the production of a super absorbent polymer. As a non-limiting example, as the polymerization initiator, a thermal polymerization initiator, a photo-polymerization initiator or the like may be used depending on the polymerization method. However, even in the case of the photo-polymerization method, a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, and thus, a thermal polymerization initiator may further be included.
- The photo-polymerization initiator used herein may include, for example, one or more compounds selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine and α-aminoketone. Among them, as a specific example of the acylphosphine, a commonly used lucyrin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide may be used. More various photo-polymerization initiators are well disclosed in "UV Coatings: Basics, Recent Developments and New Application" written by Reinhold Schwalm, (Elsevier, 2007), p 115, the content of which is incorporated herein by reference.
- Moreover, as the thermal polymerization initiator, one or more compounds selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specific examples of the persulfate-based initiator may include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), and the like. In addition, examples of the azo-based initiator may include 2,2-azobis(2-amidinopropane)dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 4,4-azobis-(4-cyanovaleric acid) or the like. More various thermal polymerization initiators are well disclosed in "Principle of Polymerization" written by Odian, (Wiley, 1981), p 203, the content of which is incorporated herein by reference.
- The polymerization initiator may be included in a concentration of about 0.001 to 1% by weight based on the monomer composition. That is, when the concentration of the polymerization initiator is too low, the polymerization rate may become slow and a large amount of residual monomer may be extracted in the final product, which is not preferable. On the other hand, when the concentration of the polymerization initiator is too high, the polymer chains constituting the network become short, and thus the extractable contents are increased and physical properties of the polymer may deteriorate such as a reduction in absorption under pressure.
- Meanwhile, the monomer composition may include a crosslinking agent ("internal crosslinking agent") to improve physical properties of the polymer by polymerization of the water-soluble ethylenically unsaturated monomer. The crosslinking agent is used for internal crosslinking of the hydrogel polymer, and is used separately from a surface crosslinking agent described below.
- Particularly, in the production method of the another embodiment, the above-mentioned two or more internal crosslinking agents, for example, the polyol poly(meth)acrylate first internal crosslinking agent and the allyl(meth)acrylate-based second internal crosslinking agent can be used together to obtain a hydrogel polymer having a higher gel strength, for example, a gel strength of 10000 Pa or more, or 11000 Pa or more, or 120000 Pa or more, and but not particularly limited thereto, 50000 Pa or less, or 40,000 Pa or less, or 38,000 Pa or less.
- More specifically, as the first internal crosslinking agent, at least one selected from the group consisting of trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene di(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentacrylate, glycerin tri(meth)acrylate, and pentaerythritol tetraacrylate may be used, and as the second internal crosslinking agent, allyl(meth)acrylate, allylacrylate, and the like may be used.
- Further, the first internal crosslinking agent may be added in an amount of 0.4 to 1 part by weight, or 0.5 to 0.9 parts by weight, or 0.6 to 0.8 parts by weight, based on 100 parts by weight of the entire monomer composition including the internal crosslinking agent, the monomer and the like. The second internal crosslinking agent may be added in an amount of 0.008 to 0.5 parts by weight, or 0.01 to 0.1 parts by weight, or 0.01 to 0.05 parts by weight, based on 100 parts by weight of the entire monomer composition. In this way, by controlling the composition such as the type and content range of the internal crosslinking agent and also controlling the water content of the hydrogel polymer to be described later, a hydrogel polymer exhibiting a gel strength of 10,000 Pa or more can be obtained more effectively, and a super absorbent polymer satisfying the physical properties of one embodiment can be obtained more effectively. However, if the content of the internal crosslinking agent is excessively large, the basic absorption performance of the super absorbent polymer may be deteriorated.
- In addition, the monomer composition may further include an additive such as a thickener, a plasticizer, a preservation stabilizer, an antioxidant, etc., if necessary.
- Further, such monomer composition can be prepared in the form of a solution in which raw materials such as the above-described monomer, polymerization initiator, internal crosslinking agent, etc. are dissolved in a solvent.
- In this case, any usable solvent can be used without limitation in the constitution as long as it can dissolve the above-mentioned raw materials. Examples of the solvent may include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethylether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N,N-dimethylacetamide, or a mixture thereof.
- Further, the formation of the hydrogel polymer through polymerization of the monomer composition may be performed by a general polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method are largely classified into a thermal polymerization and a photo-polymerization according to the type of the polymerization energy source, and the thermal polymerization may be carried out in a reactor like a kneader equipped with agitating spindles and the photo-polymerization may be carried out in a reactor equipped with a movable conveyor belt.
- As an example, the monomer composition is injected into a reactor like a kneader equipped with the agitating spindles, and thermal polymerization is performed by providing hot air thereto or heating the reactor, thereby obtaining the hydrogel polymer. In this case, the hydrogel polymer, which is discharged from the outlet of the reactor according to the type of agitating spindles equipped in the reactor, may be obtained as particles with a size of centimeters or millimeters. Specifically, the hydrogel polymer may be obtained in various forms according to the concentration of the monomer composition injected thereto, the injection speed, or the like, and the hydrogel polymer having a (weight average) particle diameter of 2 to 50 mm may be generally obtained.
- As another example, when the photo-polymerization of the monomer composition is performed in a reactor equipped with a movable conveyor belt, a sheet-shaped hydrogel polymer may be obtained. In this case, the thickness of the sheet may vary depending on the concentration of the monomer composition injected thereto and the injection speed, and the polymer sheet is preferably controlled to have typically a thickness of 0.5 to 10 cm in order to secure the production speed or the like while enabling a uniform polymerization of the entire sheet.
- In this case, the hydrogel polymer obtained by the above-mentioned method may have a water content of 38 to 60% by weight or 40 to 55% by weight. The "water content" as used herein means a weight occupied by moisture with respect to a total weight of the hydrogel polymer, which may be the value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer. Specifically, the water content can be defined as a value calculated by measuring the weight loss due to evaporation of moisture in the polymer in the drying process by raising the temperature of the polymer through infrared heating. At this time, the drying conditions may be determined as follows: the drying temperature is increased from room temperature to about 180°C and then the temperature may be maintained at 180°C, and the total drying time may be set to 20 minutes, including 5 minutes for the temperature rising step.
- Not only the water content of the hydrogel polymer is adjusted to the above-described ranges and thus the gel strength before pulverization of 10000Pa described above may be achieved more effectively, but also the subsequent gel pulverization can be carried out more effectively. Specifically, the hydrogel polymer is introduced into a gel pulverizer in the state where the water content has been adjusted. As the gel pulverization conditions described below are adjusted, not only the high gel strength range before gel pulverization can be more easily achieved, the gel strength after gel pulverization can be maintained at 35% to 95%, or 50% to 90%, or 60% to 88% of the gel strength before the pulverization. As a result, the inner surface area of the base polymer powder and the super absorbent polymer containing the same is widened, whereby the super absorbent polymer exhibits excellent absorption rate, and also the base polymer powder and the super absorbent polymer can maintain high strength and so exhibit excellent liquid permeability and the like.
- Meanwhile, after the hydrogel polymer is formed by the above-mentioned crosslinking polymerization, the hydrogel polymer with controlled water content is gel-pulverized. Such gel pulverization can be carried out so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization. In a specific example, the gel strength after gel pulverization may be from 5000Pa to 30000Pa, or from 10000Pa to 28000Pa. Thereby, a super absorbent polymer that satisfies the physical properties of the one embodiment can be more effectively obtained.
- The pulverizing device used in the pulverization step is not limited in its constitution, but specific examples thereof may include any one selected from the group consisting of a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper and a disc cutter. However, it is not limited to the above-described example.
- On the other hand, during the gel pulverization of the hydrogel polymer, a shear force and a compressive force is applied to the hydrogel polymer. In the production method of another embodiment, the gel strength range after the gel pulverization described above can be achieved by controlling the gel pulverization conditions.
- More specifically, the gel pulverization can be carried out inside a pulverizer including an extruder equipped with a perforated plate such as a screw extruder. At this time, a plurality of holes formed in the perforated plate may have a diameter of 9 to 18 mm, or 10 to 15 mm, whereby the gel pulverization can be carried out by pushing the hydrogel polymer through such a perforated plate and an extruder. Thereby, the hydrogel polymer can maintain an adequate level of gel strength even after gel pulverization, and the gel pulverization is effectively carried out so that the polymer after pulverization can have a large surface area.
- That is, when the above-mentioned gel pulverization is carried out, the surface area of the pulverized hydrogel polymer is remarkably increased. Specifically, in the pulverized hydrogel polymer, the percentage of the number of sheared particles is 0.40 or more and 0.95 or less. The "sheared particle" means a particle having three or more concave portions or holes with a depth of 10 µm or more observed on the pulverized hydrogel polymer particle, and the "number ratio of the sheared particles" means the number of the sheared particles relative to the total number of the hydrogel polymer particles. As described above, the sheared particles are produced and the surface area is widened, so that the physical properties of the super absorbent polymer can be more improved and the super absorbent polymer satisfying the various physical properties of one embodiment can be produced more effectively.
- On the other hand, the pulverization of the hydrogel polymer may be performed such that the hydrogel polymer has a particle diameter of 0.1 mm to 10 mm. That is, in order to increase the drying efficiency, the hydrogel polymer is preferably pulverized into particles with a size of 10 mm or less. However, since a phenomenon of agglomeration between particles may occur during excessive pulverization, the hydrogel polymer is preferably pulverized into particles with a size of 0.1 mm or more.
- In addition, since gel pulverization of the hydrogel polymer is performed out in a state of relatively low water content, a phenomenon in which the hydrogel polymer adheres to the surface of the pulverizing device can occur. In order to minimize such a phenomenon, steam, water, surfactant, agglomeration preventing agent (for example, clay, silica, etc.); persulfate-based initiators, azo-based initiators, hydrogen peroxide, thermal polymerization initiator, epoxy-based crosslinking agent, a diol crosslinking agent, a crosslinking agent containing difunctional, trifunctional or higher polyfunctional acrylate, crosslinking agent with mono-functionality containing a hydroxyl group or the like can be added to the hydrogel polymer as needed.
- After the gel pulverization described above, the hydrogel polymer can be dried. The drying can be carried out at a temperature of 120 to 250°C, preferably 140 to 200°C, more preferably 150 to 190°C. In this case, the drying temperature can be defined as the temperature of the heating medium provided thereto for drying, or the internal temperature of the drying reactor including the heating medium and the polymer during the drying process. If the drying temperature is low, and therefore the drying time becomes long, the efficiency of the process may be deteriorated. In order to prevent this problem, the drying temperature is preferably 120°C or higher. In addition, when the drying temperature is higher than necessary, the surface of the hydrogel polymer is excessively dried, and the occurrence of fine powders may be increased during the subsequent pulverization process and the physical properties of the polymer finally formed may be deteriorated. In order to prevent this problem, therefore, the drying temperature is preferably 250°C or lower.
- In this case, the drying time in the drying step is not particularly limited, but it may be controlled to 20 to 90 minutes at the above drying temperature, in consideration of the process efficiency and the physical properties of the polymer.
- The drying can be carried out using a conventional medium, and for example, the drying may be carried out by the methods of subjecting the pulverized hydrogel polymer to hot air supply, infrared irradiation, microwave irradiation, ultraviolet irradiation or the like.
- The drying is preferably carried out so that the dried polymer has a water content of about 0.1% to 10% by weight. That is, if the water content of the dried polymer is less than 0.1% by weight, production costs may be increased due to excessive drying and degradation of the crosslinked polymer may occur, which is not desirable. In addition, if the water content of the polymer is more than 10% by weight, defects may occur in a subsequent process, which is not desirable.
- After the drying, the dried polymer can be pulverized. Thereby, the particle diameter and surface area of the pulverized polymer can be controlled within an appropriate range. The pulverization can be carried out such that the pulverized polymer has a particle diameter of 150 to 850 µm.
- Examples of the pulverizing device that can be used herein include a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jog mill or the like.
- Further, in order to control the physical properties of the super absorbent polymer finally produced, the step of selectively classifying particles having a particle diameter of 150 to 850 µm in the polymer particles obtained through the above-mentioned pulverization step may be further performed.
- On the other hand, through the classification, polymer particles (fine powder) having a particle diameter of less than 150 µm can be granulated with a solvent (for example, aqueous solvent such as water) usable in the crosslinking polymerization step to prepare a fine powder re-granulated body. The fine powder re-granulated body may be added and mixed to the super absorbent polymer before the drying, for example, to the super absorbent polymer just before or just after the gel pulverization step, and between the drying step.
- The fine powder re-granulated body may be mixed in an amount of 10 to 30 parts by weight, or 15 to 28 parts by weight based on 100 parts by weight of the hydrogel polymer before drying. Due to the addition of such fine powder re-granulated body, the internal surface area of the base polymer powder and the super absorbent polymer can be more widened and the super absorbent polymer can exhibit a more enhanced absorption rate. In addition, the strength of the base polymer powder and the super absorbent polymer is controlled to an appropriate range by introducing the fine powder re-granulated body within the above-mentioned content range, and thus various physical properties of one embodiment can be achieved more effectively.
- On the other hand, after the base polymer powder is produced through the classification step described above, the base polymer powder can be subjected to heat treatment and surface crosslinking in the presence of a surface crosslinking agent to form super absorbent polymer particles.
- The surface crosslinking induces a crosslinking reaction on the surface of the base polymer powder in the presence of a second crosslinking agent (surface crosslinking agent). Through such surface crosslinking, a surface modified layer (surface crosslinked layer) is formed on the surface of the pulverized polymer particles.
- The surface crosslinking may be performed by a method of mixing a solution containing a second crosslinking agent (surface crosslinking agent) with the base polymer powder followed by a crosslinking reaction.
- Herein, the surface crosslinking agent is a compound capable of reacting with a functional group of the polymer, and may be an alkylene carbonate-based compound or a polyhydric alcohol-based compound. An alkylene carbonate having 2 to 5 carbon atoms is preferable. More preferably, ethylene carbonate can be used as the surface crosslinking agent. In addition to the surface crosslinking agent, silica, clay or the like can be further used. Further, in order to control the penetration rate and depth of the surface crosslinking agent, an acidic compound, a polymer, or the like can be further added, if necessary.
- At this time, the content of the surface crosslinking agent may be appropriately controlled according to the kind of crosslinking agent, reaction conditions, etc., and may be preferably adjusted to 0.001 to 5 parts by weight based on 100 parts by weight of the base polymer powder. If the content of the surface crosslinking agent is excessively low, the surface modification may not be properly performed, and the physical properties of the final polymer may be deteriorated. Conversely, if an excess amount of the surface crosslinking agent is used, the basic absorption capacity of the polymer may rather decrease due to excessive surface crosslinking reaction, which is not preferable.
- On the other hand, the surface crosslinking step may be performed by a conventional method such as a method in which the surface crosslinking solution containing the surface crosslinking agent and the base polymer powder are added to a reaction vessel and mixed, a method in which the surface crosslinking solution containing the surface crosslinking agent is sprayed onto the base polymer powder, a method in which the base polymer powder and the surface crosslinking solution are continuously supplied in a continuously operating mixer and mixed, and the like.
- Moreover, when adding the surface crosslinking agent, water may be further added. Thus, adding the surface crosslinking agent and water together may induce uniform dispersion of the surface crosslinking agent, prevent the aggregation phenomenon of the base polymer powder, and further optimize the penetration depth of the surface crosslinking agent to the base polymer powder. In consideration of these objects and effects, the content of water to be added together with the surface crosslinking agent may be adjusted to 0.5 to 10 parts by weight based on 100 parts by weight of the base polymer powder.
- The surface crosslinking step may be proceeded at a temperature of 100 to 250° C. Further, the surface crosslinking can be proceeded for 1 minute to 120 minutes, preferably 1 minute to 100 minutes, more preferably 10 minutes to 80 minutes. That is, in order to prevent the polymer particles from being damaged to thereby decrease their physical properties during excessive reaction while inducing the minimum surface cross-linking reaction, the surface crosslinking step may be carried out under the above-mentioned conditions.
- The super absorbent polymer according to the present invention can exhibit more improved absorption rate and liquid permeability, while maintaining excellent basic absorption performance, and thus is preferably used for hygienic materials such as diapers having a thinner thickness.
- Hereinafter, preferred examples are provided for better understanding of the invention. However, these Examples are given for illustrative purposes only and are not intended to limit the scope of the present invention thereto.
- As the manufacturing apparatus of a super absorbent polymer, a continuous manufacturing apparatus comprising a polymerization step, a hydrogel pulverizing step, a drying step, a pulverization step, a classification step, a surface cross-linking step, a cooling step, a classification step, and a transport step connecting respective steps can be used.
- 0.7 parts by weight (7000 ppm) of polyethylene glycol diacrylate (weight average molecular weight: ∼500 g/mol) as an internal crosslinking agent, 0.015 part (150 ppm) of allyl methacrylate and 0.01 part by weight of IRGACURE 819 as a photoinitiator were mixed to prepare a monomer solution. Subsequently, while continuously supplying the monomer solution by a metering pump, 160 parts by weight of a 24 wt % aqueous solution of sodium hydroxide was continuously subjected to line mixing to prepare an aqueous monomer solution. At this time, the temperature raised by the neutralizing heat was adjusted to 40°C. Further, 6 parts by weight of a 4 wt% aqueous solution of sodium persulfate was continuously subjected to line mixing, and then continuously supplied to a continuous polymerization reactor having a planar polymerization belt with a darn at each end. Thereafter, UV light was irradiated for 1 minute, and further thermal polymerization was carried out for 2 minutes to prepare a hydrogel. The water content of the hydrogel was confirmed to be 45% by weight.
- The hydrogel was cut to have an average size of about 300 mm or less, and then introduced into a pulverizer (equipped with a perforated plate including a plurality of holes having a diameter of 11 mm) together with a fine powder re-granulated body as shown in Table 1 below and pulverized under the respective conditions. Herein, the fine powder re-granulated body used the fine powder re-granulated body prepared in step 4 below, and the input ratio is shown in Table 1 as 20 weight % relative to the hydrogel.
- Then, the hydrogel pulverized in step 2 were dried in an oven capable of shifting airflow up and down. The hydrogel was uniformly dried by flowing hot air at 180°C from the bottom to the top for 15 minutes and from the top to the bottom for 15 minutes, so that the dried product had a water content of about 2% or less.
- The polymer dried in step 3 was pulverized using a pulverizer and classified to obtain a base polymer having a size of 150 to 850 µm. On the other hand, through the above classification, the polymer particles having a particle size of less than 150 µm was granulated with water and used for the fine powder re-granulated body of step 2 described above.
- Then, 100 parts by weight of the base polymer prepared in step 4 was mixed with a crosslinking agent solution containing 4 parts by weight of water and 1 part by weight of ethylene carbonate and then subjected to a surface crosslinking reaction at 180°C for 40 minutes. Then, the obtained product was cooled and classified to obtain a surface-crosslinked super absorbent polymer having a particle diameter of 150 to 850 µm.
- A super absorbent polymer was prepared in the same manner as in Example 1, except that the content range of the internal crosslinking agent, the hole diameter of the perforated plate provided in the gel pulverizer, the water content of the hydrogel and the input ratio of the fine powder re-granulated body were changed as shown in Table 1 below.
- In the following Examples 1 to 8 and Comparative Examples 1 to 4, the gel strength of the hydrogel before and after the gel pulverization was measured by the method summarized in the following, and the measurement results are summarized and shown together in Table 1 below.
- First, a hydrogel sample to be measured (a hydrogel sheet before gel pulverization and a hydrogel after gel pulverization) was prepared to have a diameter of about 2.5 cm and a thickness of about 2 to 5 mm. The prepared sample was loaded on a microbalance, and an appropriate amount of distilled water was evenly sprayed using a sprayer (At this time, the initial water content of the hydrogel was measured in advance (water content measuring instrument condition: 180°C, 40 minutes), and the amount of water required to match the initial water content was calculated). In order to uniformly adjust the water content inside the sample, it was sealed in vinyl and stored at room temperature for 12 hours or more.
- A hydrogel sample with controlled water content was loaded between two plates of the rheometer (ARES-G2), and the gap between the two plates was properly adjusted by pressing the plates with a force of 3 N so that the sample was contacted at the front face of the plate. Rest time was given for 5 minutes to stabilize the sample. At the time of measurement, first, a strain in the linear viscoelastic regime section where the storage modulus (G') and the loss modulus (G") were constant was found while increasing the strain at a frequency of 10 rad/s.
- After finding the strain value (usually 0.1%) in the linear regime section, the viscoelasticity (G', G") was measured for 60 seconds at a constant frequency (10 rad/s). After three or more measurements, the average value of G' was calculated as the gel strength (G').
[Table 1] Internal crosslinking agent (P/A*; ppm) Hole diameter of perforated plate (mm) Water content of hydrogel (wt%) Input ratio of fine powder regranulated body (wt%) Gel strength of hydrogel before gel pulverization (Pa) Gel strength of hydrogel after gel pulverization (Pa) Gel strength ratio before and after gel pulverization (%) Example 1 7000/150 11 45 20 23300 18500 79.4 Example 2 7000/150 11 40 20 27700 20800 75.1 Example 3 7000/150 11 50 20 19200 15900 82.8 Example 4 8000/200 11 40 20 37400 26900 71.9 Example 5 5000/100 11 50 20 15600 10300 66.0 Example 6 7000/150 11 45 20 23100 17600 76.2 Example 7 7000/150 13 40 25 27800 21500 77.3 Example 8 7000/150 16 40 20 27600 23700 85.9 Comparative Example 1 5000/100 11 65 20 6500 6000 92.3 Comparative Example 2 7000/150 7 45 20 23200 7900 34.1 Comparative Example 3 7000/150 20 45 20 23300 22600 97.0 Comparative Example 4 3000/50 11 45 20 8500 7000 82.4 * Internal crosslinking agent P/A: polyethylene glycol diacrylate/allymethacrylate - Referring to Table 1, it was confirmed that in Examples 1 to 8, the kind, content, water content and the like of the internal crosslinking agent are adjusted so that the hydrogel has a gel strength of 10,000 Pa or more, and the hole diameter and the water content of the perforated plate of the gel pulverizer are adjusted so that the gel strength after gel pulverization satisfies the range of 35 to 95% of the gel strength before gel pulverization.
- In contrast, it was confirmed that in Comparative Example 1, the water content of the hydrogel before gel pulverization is excessively high, so that the hydrogel before and after gel pulverization shows a low gel strength. Even in Comparative Example 4, the content of the internal crosslinking agent is excessively low, so that the hydrogel before gel pulverization shows a low gel strength. Further, in Comparative Examples 2 and 3, the hole diameter of the perforated plate of the gel pulverizer is not maintained at an appropriate level, and so the gel strength after the gel pulverization deviates from the appropriate range.
- The physical properties of the super absorbent polymer prepared in Examples and Comparative Examples were measured and evaluated by the following methods.
- The centrifuge retention capacity(CRC) by water absorption capacity under a non-loading condition was measured for the super absorbent polymers of Examples and Comparative Examples in accordance with EDANA (European Disposables and Nonwovens Association) recommended test method No. WSP 241.3. Wo (g, about 0.2 g) of the super absorbent polymer was uniformly put in a nonwoven fabric-made bag, followed by sealing. Then, the bag was immersed in a physiological saline solution composed of 0.9 wt% aqueous sodium chloride solution at room temperature. After 30 minutes, water was removed from the bag by centrifugation at 250 G for 3 minutes, and the weight W2(g) of the bag was then measured. Further, the same procedure was carried out without using the super absorbent polymer, and then the resultant weight W1(g) was measured. Using the respective weights thus obtained, CRC (g/g) was calculated according to the following Equation 1, thereby confirming the centrifuge retention capacity.
- The physiological saline flow conductivity (SFC) was measured and calculated according to the method disclosed in columns 54 to 59 of
U.S. Patent No. 5,562,646 . - 9 g of sodium chloride and 0.1 g of Lorodac (main component: linear alcohol ethoxylate having 12 to 14 carbon atoms, CAS #68439-50-9) were dissolved in 1 L of distilled water to make an aqueous solution, and the T-20 was calculated and measured with the time required for absorbing 1 g of the super absorbent polymer to 20 g of this aqueous solution under pressure of 0.3 psi. Specific measurement methods of T-20 were described in detail on pages 13 to 18 of European Patent Publication No.
2535027 . - The FSR of the base polymer powder or the super absorbent polymer was measured and calculated by using those classified into #30 to #50 (for example, those having a particle diameter of 300 to 600 µm) according to the method disclosed on pages 22 to 23 of European Patent Publication No.
2535027 . - The measurement was performed after absorbing the super absorbent polymer to a physiological saline solution (0.9 wt% aqueous sodium chloride solution) under pressure of 0.3 psi, which was measured and calculated as a fixed height absorption (FHA) (20 cm). The other specific measurement and calculation method was performed according to the method disclosed in Examples of
US Patent No. 7,108,916 . - The physical property values of Examples 1 to 8 and Comparative Examples 1 to 4 measured by the above method are summarized in Table 2 below.
[Table 2] CRC FHA FSR SFC T-20 Unit g/g g/g g/g/s 10-7cm3·s/g s Example 1 28.5 24.5 0.32 55 140 Example 2 28.1 24.2 0.33 53 133 Example 3 29.0 24.6 0.30 56 145 Example 4 27.1 24.0 0.36 63 123 Example 5 28.8 23.7 0.30 47 147 Example 6 28.3 24.3 0.32 51 139 Example 7 28.6 24.5 0.30 55 146 Example 8 28.7 24.6 0.29 57 154 Comparative Example 1 29.0 22.0 0.19 18 233 Comparative Example 2 25.6 21.1 0.33 23 134 Comparative Example 3 27.1 23.3 0.18 57 241 Comparative Example 4 29.1 22.8 0.20 18 213 - Referring to Table 2, it was confirmed that in the case of Examples 1 to 8, the basic absorption performance defined by CRC is excellent, the suction force under pressure defined by FHA and the liquid permeability defined by the SFC are excellent, and the absorption rates defined by T-20 or FSR are also excellent.
- In contrast, it was confirmed that in the case of Comparative Examples 1 to 4, at least one of the liquid permeability, the absorption rate or the absorption under pressure is poor as compared with Examples.
Claims (12)
- A super absorbent polymer comprising:a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; anda surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent,wherein the super absorbent polymer has the following features:a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g,a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 (·10-7 cm3·s/g) or more, andT-20 of 180 seconds or less which indicates the time required for absorbing 1 g of the super absorbent polymer to 20 g of aqueous solution of 0.9 wt% sodium chloride and 0.01 wt% alcohol ethoxylate having 12 to 14 carbon atoms under pressure of 0.3 psi.
- The super absorbent polymer according to claim 1, wherein the centrifuge retention capacity (CRC) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 30 minutes is 26 g/g to 34 g/g.
- The super absorbent polymer according to claim 1, wherein the super absorbent polymer has the free swell rate (FSR) of 0.25 g/g/s or more when 1 g of the super absorbent polymer absorbs 20 g of a 0.9 wt% aqueous sodium chloride solution.
- The super absorbent polymer according to claim 1, wherein the water-soluble ethylenically unsaturated monomer includes at least one selected from the group consisting of an anionic monomer of acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloyl ethane sulfonic acid, 2-methacryloyl ethane sulfonic acid, 2-(meth)acryloyl propane sulfonic acid, or 2-(meth)acrylamide-2-methylpropane sulfonic acid, and a salt thereof; a nonionic hydrophilic monomer of (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxypolyethyleneglycol(meth)acrylate, or polyethyleneglycol(meth)acrylate; and an unsaturated monomer containing amino group of (N,N)-dimethylaminoethyl(meth)acrylate or (N,N)-dimethylaminopropyl(meth)acrylamide, and a quaternary compound thereof.
- The super absorbent polymer according to claim 1, wherein the first crosslinked polymer includes a polymer in which the monomer is crosslinked in the presence of a polyolpoly(meth)acrylate-based first internal crosslinking agent selected from the group consisting of trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycoldi(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentacrylate, glycerin tri(meth)acrylate, and pentaerythritol tetraacrylate; and an allyl(meth)acrylate-based second crosslinking agent.
- The super absorbent polymer according to claim 1, having a particle diameter of 150 to 850 µm.
- A super absorbent polymer comprising:a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; anda surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent,wherein the super absorbent polymer has the following features:a fixed height absorption (FHA) (20 cm) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) of 22.5 g/g to 29 g/g,a centrifuge retention capacity (CRC) for a physiological saline solution (0.9 wt% aqueous sodium chloride solution) for 30 minutes of 26 g/g to 34 g/g,a saline flow conductivity (SFC) for a physiological saline solution (0.685 wt% aqueous sodium chloride solution) of 35 (·10-7 cm3·s/g) or more, anda free swell rate (FSR) of 0.25 g/g/s to 0.40 g/g/s when 1 g of the super absorbent polymer absorbs 20 g of a 0.9 wt% aqueous sodium chloride solution.
- A method for producing a super absorbent polymer comprising the steps of:performing crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent to form a hydrogel polymer containing a first crosslinked polymer and having a gel strength pf 10000 Pa or more;performing gel pulverization of the hydrogel polymer so that the gel strength after pulverization becomes 35% to 95% of the gel strength before pulverization;drying, pulverizing and classifying the gel pulverized hydrogel polymer to form a base polymer power; andheat-treating and surface-crosslinking the base polymer powder in the presence of a surface crosslinking agent to form a super absorbent polymer particle.
- The method for producing a super absorbent polymer according to claim 8, wherein the internal crosslinking agent includes a polyolpoly(meth)acrylate-based first internal crosslinking agent and an allyl(meth)acrylate-based second crosslinking agent,
the first internal crosslinking agent is contained in an amount of 0.4 to 1 part by weight, based on 100 parts by weight of the monomer composition including the internal crosslinking agent and the monomer, and the second internal crosslinking agent is contained in an amount of 0.008 to 0.5 parts by weight, based on 100 parts by weight of the monomer composition. - The method for producing a super absorbent polymer according to claim 8, wherein in the gel pulverization step, the hydrogel polymer has a water content of 38 to 60% by weight, and the hydrogel polymer is subjected to a gel pulverization through an extruder equipped with a perforated plate having a plurality of holes with a diameter of 9 to 18 mm.
- The method for producing a super absorbent polymer according to claim 8, further comprising the steps of:recovering a fine powder having a particle diameter of less than 150 µm after the classification step;re-granulating the fine powder in the presence of an aqueous solvent; andmixing the fine powder re-granulated body with the hydrogel before the drying,wherein the re-granulated body is used in an amount of 10 to 30 parts by weight based 100 parts by weight of the hydrogel polymer before the drying.
- The method for producing a super absorbent polymer according to claim 8, wherein the surface crosslinking agent includes an alkylene carbonate-based compound or a polyhydric alcohol-based compound.
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US20200009530A1 (en) | 2020-01-09 |
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